Pure fluidic de-coupler

ABSTRACT

This invention relates to pure fluidic units and devices, and more particularly to impedance-matching in pure fluid devices. Accordingly a pure fluid device is provided for the purpose of de-coupling one fluidic unit from another when they are staged. The fluidic de-coupler of the instant invention utilizes a novel two-sided vent design in the receiver line of the fluidic unit. Specifially, a square velocity profile is obtained in the receiver line by passing the flow in the receiver through an expanded portion of the line, that is, a plenum, then through a moderate contraction having a specified width W. Vents are then provided to either side of the receiver line down stream from the contraction, the vents having a width of 3W. A catcher portion of the receiver line is disposed further down stream from the vents, the catcher portion having a width of 2W, or double the receiver nozzle or contraction width. The square profile jet issuing from the nozzle of the receiver entrains about 100 percent flow over a 3W distance. This velocity profile does not decay over the distance of the actual vents provided in the de-coupler. This decoupler design incorporating 2W as a width of the catcher is such to entrain substantially all of the flow. The de-coupler is designed such that the catcher length is 15W. This catcher length maximizes the block load pressure recovery such that the flow distributes itself evenly in the catcher.

United States Patent [1 1 Drzewiecki [11] 3,811,476 [451 May 21, 1974PURE FLUIDIC DE-COUPLER [75] Inventor: Tadeusz M. Drzewiecki,

Gaithersburg, Md.

[73] Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

[22] Filed: Apr. 27, 1973 [21] Appl. No.: 355,126

[52] U.S. Cl. 137/842 [51] -Int. Cl. FlSc 1/00 [58] Field of Search137/842, 819

[56] References Cited UNITED STATES PATENTS 3,636,964 l/1972 Colamussiet al 137/842 3,461,895 8/1969 Colston 137/842 X 3,561,463 2/1971 Beeken137/842 X 3,574,309 4/1971 Kinner 137/842 X Prima ry Examiner-William R.Cline Attorney, Agent, or Firm-Edward J. Kelly; Herbert Ber]; SaulElbaum [57] ABSTRACT This invention relates to pure fluidic units anddevices,

and more particularly to impedance-matching in pure fluid devices.Accordingly a pure fluid device is provided for the purpose ofde-coupling one fluidic unit from another when they are staged. Thefluidic decoupler of the instant invention utilizes a novel twosidedvent design in the receiver line of the fluidic unit. Specifially, asquare velocity profile is obtained in the receiver line by passing theflow in the receiver through an expanded portion of the line, that is, aplenum, then through a moderate contraction having a specified width W.Vents are then provided to either side of the receiver line down streamfrom the con-' traction, the vents having a width of 3W. A catcherportion of the receiver line is disposed further down stream from thevents, the catcher portion having a width of 2W, or double the receivernozzle or contraction width. The square profile jet issuing from thenozzle of the receiver entrains about 100 percent flow over a 3Wdistance. This velocity profile does not decay over the distance of theactual vents provided in the de-coupler. This de-coupler designincorporating 2W as a width of the catcher is such to entrainsubstantially all of the flow. The de-coupler is designed such that thecatcher length is 15W. This catcher length maximizes the block loadpressure recovery such that the flow distributes itself evenly in thecatcher.

7 Claims, 4 Drawing Figures PURE FLUIDIC DE-COUPLER RIGHTS OF THEGOVERNMENT The invention described herein may be manufactured, used, andlicensed by or for the US. Government for governmental purposes withoutthe payment to the inventor of any royalty thereon.

BACKGROUND OF THE INVENTION It is of great concern to the fluidicdesigner to decouple one fluidic unit from another when they are staged.Heretofore, coupling devices for pure fluid units have not allowed fullinvestigation of back load sensitive devices because previously only aportion of the P-Q curves could be examined since the unit would becomeeither unstable or in a new state (flipped).

In the past in order to examine the full range of pressure flow,designers have put vents into the receiver lines of fluid amplifiers.This kind of venting, however, was not efficient in most cases and inothers did not decouple well at all. Previously, designs of in linevents have incorporated bilaterally symmetrical vents perpendicular tothe flow of fluid. Other designs have incorporated large plenatangential to the flow of fluid within the receiver line. And, evenother types of units have incorporated vents in the operating region.None of these units de-couple with the respect to the uniqueness of theoperating flow field. These units do, however, help in the flow recoveryto some extent, but the fact that they only entrain on one side meansthat they are not as efficient in jet pumping as a symmetrical(two-sided) vent.

Fluids in fluid jet amplifiers have three significant properties; mass,viscosity, and compressibility. Aside from basic energy flux associatedwith the jets, significant manifestation of these properties includewave motions, energy dissipation, and gross turbulence. These phenomenaare partially beneficial, and yet also introduce inherent limitations tothe operation of fluid amplifiers.

Wave motion in fluid-amplifiers is a factor frequently causingunsatisfactory operation. Its mechanism is not well understood but theseriousness of the dynamic instabilities which result are clearlydiscernable. Most of these effects can be traced to the interaction ofthe amplifier with its inputs (source impedance-matching) or with itsoutputs (load impedance-matching).

In the design of fluid-amplifier systems, it is desirable that eachamplifier or element in the system have matching impedances. Actually,the existing problem in the design of fluid system is feeding the outputof a first device to the controls of a second device when the physicalconstruction of the second device limits the flow below a certain value.Since the output dimensions of a given unit are generally larger thanthe controls, it becomes impossible to operate one into the other wheretwo units are identical. Actually the second driven device, must beseveral times larger as a minimum. Without a dump, or bleed, the systembecomes filled with fluid and ceases to operate.

Another problem is the loading effects in sensitive circuits, forexample, a change in the load can be reflected to the interactionchamber of a fluid oscillator causing a change in frequency.

It is therefore an object of this invention to provide a new and novelmeans for de-coupling one fluidic unit from another such that spurioussignals are not exchanged between stages.

It is another object of this invention to provide a means for decouplingone fluidic unit from another wherein back stages are not loaded.

It is a primary object of this invention to provide a receiverdecouplingmeans which optimizes a flow field such that only one flowfield is utilized as opposed to an infinity of flow fields eachdepending on the down stream impedance.

It is yet an additional object of this invention to provide a new andnovel fluidic receiver de-coupler which provides a square velocityprofile at the end of the receiver.

It is still an additional object of this invention to provide adecoupling means for providing a velocity profile which will not decayappreciably over a short vent.

These and other objects of the present invention will become more fullyapparent with reference to the following specifications and drawingwhich relate to a preferred embodiment of the present invention.

- SUMMARY OF THE INVENTION In accordance with this invention a new andnovel two-sided vent decoupling for effectively de-coupling two stagefluidic elements is provided. The fluidic decoupler of the instantinvention utilizes a novel twosided vent design in the receiver line.Specifically, a square velocity profile is obtained in the receiver lineby passing the flow in the receiver through an expanded portion of theline, i.e., a plenum, and then through a moderate contraction having awidth W. Vents are then provided to either side of the receiver linedown stream from the contraction, the vents having a width of 3W. Acatcher portion of the receiver line is disposed further down streamfrom the vents, the catcher portion having a width 2W or double thereceiver nozzle contraction width. This arrangement provides a squareprofile jet which enables entrainment of about percent flow over a 3Wdistance. The velocity profile does not decay over the distance of theactual vents provided. The particular catcher width utilized is such asto entrain substantially all of the flow. The catcher length is designedto be 15W. This particular catcher length maximizes the block loadpressure recovery such that the flow distributes itself evenly in thecatcher.

BRIEF DESCRIPTION OF THE DRAWING The specific nature of the invention aswell as other objects, aspects, uses, and advantages thereof willclearly appear from the following description and the accompanyingdrawings, in which:

FIG. 1 shows a fluidic dynamic de-coupler employing a plenum, a nozzle,oblique vents and a catcher in accordance with the teaching of thisinvention.

FIG. 2 (a) is a graph indicating the block catcher pressurer recoverycharacteristics of the device versus pressure input.

FIG. 2(b) is a graph indicating catcher zero back pressure flow recoverycharacteristics of the decoupling device as a function of pressureinput.

FIG. 3 is a graph of the de-coupler efficiency.

DESCRIPTION OF THE PREFERRED EMBODIMENT The device and design of thepresent invention will be easily understood in its detail aspects byreference to FIG. 1 wherein there is shown a plane viewof the design andpassage ways incorporated into a pure fluid receiver decoupler. The purefluid receiver-decoupler comprises essentially an input orifice 18, achannel connected to plenum 15, a conduit, formed by tapered walls 31and 32, interconnecting plenum to nozzle 13, side vents 11 and 12,catcher 16, and vertical output vent 17.

Orifice 18 is provided for the purpose of connecting to the outputorifice of a fluidic unit. Output vent 17 is provided for the purpose ofconnecting the receiver nozzle or input of a fluidic unit. Thus, bymeans of the pure fluid receiver de-coupler the fluidic unit connectedto orifice 18 is de-coupled from a fluidic unit whose receiver inputchannel is connected at output vent 17. The pure fluid de-coupler isconstructed such that input orifice 18 is connected to channel 10.Channel 10 is comprised of walls 30 which taper away from the centralaxis of orifice 18. This taper of wall 30 forms a plenum 15 near thetermination of these walls. The plenum 15 is partially terminated by ashort chamber area comprised of walls 31 and 32. These walls 31 and 32converge and interconnect a nozzle 13 to plenum 15. Nozzle 13 iscomprised of walls 31 and 32. Oblique vents 11 and 12 are juxtaposed tonozzle 13. These vents 11 and 12 are slanted toward input orifice 18.The vents 11 and 12 are bilaterallyand symmetrically disposed withrespect to the central principal axis of the chamber 10 and the nozzle13. Walls 20 and 21 proximate to nozzle 13 join walls 33 and 34 of thenozzle 13 and form the outside surface thereof. The flow from the nozzle13 is entrapped by catcher l6. Catcher 16 is symmetrically disposedabout the axis of nozzle 13 and comprises walls 14 and 24. The end ofthe catcher l6 proximate to the nozzle 13 is terminated by walls 19- and22 of vents 11 and 12, respectively. In particular wall 14 of catcher 16is terminated by wall 19 of vent l1 and wall 24 is terminated by wall 22of vent 12. The opposite end of catcher 16 is terminated by output vent17. Output vent 17 is designed such that it is perpendicular to the flowfrom catcher l6 and comprises a cross section of round geometry.

Referring to FIG. 1 channel 10 interconnecting orifice 18 to plenum 15is tapered such that it terminates at plenum 15 with a larger channelwidth than at orifice 18. The width of this termination of the channel10 by walls 30 thereof is 3W where W is the width of the nozzle l3.Vents 11 and 12 comprise walls separated such that each vent has achannel width of 3W. Catcher 16 of the pure fluid de-coupler is designedsuch that walls 14 and 24 comprising said catcher each have a length of15W. These walls 14 and 24 are separated by a distant of 2W.

The fluidic de-coupler of the instant invention, by utilizing a noveltwo sided vent design and plenum in the receiver line, conditions thevelocity profile such that the profile issuing from the nozzle 13 isalmost square and will not decay appreciably over the distanceequivalent to the width 3W of the vents 11 and 12. The velocity profileentering channel 10 from orifice 18 is conditioned by passing the flowfrom orifice 18 through a plenum l5 and then through a moderatecontraction provided by short tapered walls 31 and 32 connected to thewalls of channel 10. A square profile jet is produced at nozzle 13 andas it issues from nozzle 13 entrains approximately 100 percent flow overthe 3W distance of the vents 11 and 12. In anticipation of thisentrainment the catcher width is designed as 2W, i.e., double thereceiver nozzle width.

It is worthwhile to note that at'zero catcher impedance additions orextensions of the catcher prevent flow spillage. On the other hand,increasing the distant between the catcher and the receiver nozzleprovides more flow entrainment. The length of the catcher, which hasbeen found to maximize the block load pressure recovery such that theflow may distribute itself evenly in the catcher, is 15W.

The pure fluid receiver de-coupler depicted in FIG. 1 has been found tohave a blocked catcher pressure recovery of approximately percent and acatcher zero back pressure flow recovery of approximately 210 percent.These characteristics are shown specifically in FIG. 2a and 2b,respectively. In FIG. 2 (a), curve A is a plot of pressure input to thecatcher versus flow for zero back pressure and curve B is a plot of.pressure input versus flow at the output of catcher 16 for zero backpressure. In 2(b) curve E represents a plot of pressure input versusoutput for catcher 16 when it is blocked. I

FIG. 3 shows the effect of varying the down stream (output) pressure oninput flow in pressure. Curve C shows the change in the pressure inputas a function of a change in thepressure output. Curve D shows thechange in the input flow with respect to a change in the pressureoutput. The efficiency of the pure fluid decoupler depicted herein isapproximately 98 percent.

It is to be understood that the inventor does not desire to be limitedto the exact details of construction shown and described, for obviousmodifications will occur to a person who is skilled in the art thereof.

I claim as my invention:

1. A pure fluid decoupler comprising an orifice for receiving fluidflow, a channel having nonparallel walls tapering away from the centralaxis of said orifice and sharply converging, a power nozzle disposed atthe end of said channel comprisin'gmeans for issuing a jet of fluidhaving a square velocity profile, a catcher forming a passage having awidth greater than that of the nozzle axially disposed downstream fromsaid nozzle, and at least two vents connected to said catcher andbilaterally disposed with respect to the axis of said catcher.

2. The pure fluid decoupler of claim 1 wherein said I channel comprisesa plenum connected to said power nozzle, whereby fluid passing throughsaid channel also passes through said plenum.

3. The pure fluid decoupler of claim 2 wherein the greatest width ofsaid channel is approximately three times that of said nozzle.

4. The pure fluid decoupler of claim 3 wherein the width of said ventsis three times the width of said nozzle, and wherein the width of saidcatcher is twice the width of said nozzle.

S. The pure fluid decoupler of claim 4 wherein the length of saidcatcher is 15 times the width of said nozzle.

6. The pure fluid decoupler of claim 5 wherein said vents are furthercomprised of parallel walls.

7. The pure fluid decoupler of claim 6 wherein said catcher is comprisedof parallel walls.

1. A pure fluid decoupler comprising an orifice for receiving fluidflow, a channel having nonparallel walls tapering away from the centralaxis of said orifice and sharply converging, a power nozzle disposed atthe end of said channel comprising means for issuing a jet of fluidhaving a square velocity profile, a catcher forming a passage having awidth greater than that of the nozzle axially disposed downstream fromsaid nozzle, and at least two vents connected to said catcher andbilaterally disposed with respect to the axis of said catcher.
 2. Thepure fluid decoupler of claim 1 wherein said channel comprises a plenumconnected to said power nozzle, whereby fluid passing through saidchannel also passes through said plenum.
 3. The pure fluid decoupler ofclaim 2 wherein the greatest width of said channel is approximatelythree times that of said nozzle.
 4. The pure fluid decoupler of claim 3wherein the width of said vents is three times the width of said nozzle,and wherein the width of said catcher is twice the width of said nozzle.5. The pure fluid decoupler of claim 4 wherein the length of saidcatcher is 15 times the width of said nozzle.
 6. The pure fluiddecoupler of claim 5 wherein said vents are further comprised ofparallel walls.
 7. The pure fluid decoupler of claim 6 wherein saidcatcher is comprised of parallel walls.